1. Field of the Invention
The present invention relates to a manually operated pipe cutting device for plastic pipes such as A.B.S. (Acetate Butate Styrene) plastic pipe.
2. Description of the Prior Art
In order that standard plastic fittings such as A.B.S. fittings can be used without difficulty with such pipe in plumbing installations, the pipe must be round, the cut square and without burrs. An existing roller type of cutting device used for cutting copper pipe and tubes cannot be used for cutting plastic pipe since the device employs the principle of compressive yielding which the metal pipe or tube is able to accommodate. Plastic pipes including A.B.S. plastic pipe does not remain rigid and would have a tendency to `squash-up` when subjected to cutting by such a tool rendering inaccurate, difficult and time-consuming cuts.
A plastic pipe-cutting tool presently available on the market employs a pawl and rachet arrangement which mechanism provides incremental stepwise motion of a semi-circular blade. The tube or plastic pipe is inserted into an open-ended slot (much like an open-ended wrench). The semi-circular blade, ejected incrementally from inside one jaw, presses against the tube or pipe until it is cut, when the blade butts against the opposite jaw. This device accommodates a maximum 11/2 inches outside diameter of pipe. It is ideal for cutting flexible hose and the like, However it tends to squash and possibly crack semi-rigid plastic pipe such as A.B.S. pipe. This would be even more so if it were made for larger than 11/2 inches outside diameter pipes.
A device for cutting rolled-up plastic or fabric blinds or screens can be seen in U.S. Pat. No. 4,146,959 Hopper 1979. However this device employs a blade mounted on a cantilever type subsidiary member which in turn is spring loaded to apply a cutting force. This random movement of the blade could hardly provide the positive incremental cutting action required for cutting plastic pipes which are much harder.
The common practice herefore is to cut the plastic pipe with a wood-cutting saw or metal-cutting saw. These result in a rough and irregular cut which is also not square to the axis of the pipe. The rough pipe cut has to be trimmed and deburred with sandpaper or a file before a glued joint can be made with a fitting.